Mobile IP - Foreign Agent Local Routing to Mobile Networks

In previous releases of Cisco IOS software, traffic from a correspondent node to a mobile router must always go through the mobile router’s home agent (HA). The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature allows traffic from local devices attached to the foreign agent (FA) to be routed directly through the FA to the mobile networks of mobile routers that are visiting the FA’s subnets. Direct routing is accomplished by injecting routes to the mobile network into the routing table of the FA.

The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature is useful in scenarios in which a mobile router needs to receive high bandwidth traffic, such as streaming video, from a device on the local LAN of the FA. This feature can also be useful any time that the bandwidth between the FA and the HA is limited.

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Prerequisites for Foreign Agent Local Routing to Mobile Networks

Modifications to the home agent were made to support foreign agent local routing. You must be running Cisco IOS Release 12.3(7)T or higher for both the home agent and foreign agent for this feature to function properly.

Restrictions for Foreign Agent Local Routing to Mobile Networks

A security association between the home agent (HA) and the foreign agent (FA) is mandatory. FA local routing will not occur if there is no security association configured.

Information About Foreign Agent Local Routing to Mobile Networks

Foreign Agent Local Routing to Mobile Networks Feature Design

The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature allows traffic from a correspondent node on a local subnet to route directly through the foreign agent (FA) to a mobile network that is visiting the FA. This direct routing is accomplished by injecting mobile network routes into the routing table of the FA.

This feature is useful in scenarios in which a mobile router needs to receive high bandwidth traffic, such as streaming video, from a device on the local LAN of the FA. An example of such a scenario is diagrammed in the figure below.

In this scenario, a police officer has been called to a bank where an incident is occurring. The mobile router in the police officer’s car registers with the FA and connects to the video streaming server, a correspondent node, that is located inside the bank. The police officer may then watch live video of the incident that is occurring inside the bank, gaining valuable information about how to proceed with handling the incident safely.

Before the introduction of the Mobile IP - Foreign Agent Local Routing to Mobile Networks feature, the streaming video from the correspondent node in the bank would be routed from the FA to the HA, then back to the FA, and finally to the mobile router. This behavior, known as triangular routing, is not desirable for latency-sensitive applications. If a second police car arrived and wanted to watch the video as well, the already limited bandwidth between the FA and the HA would be even further taxed. The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature allows traffic from the local corresponding node to be routed directly from the FA to the mobile router, eliminating the unnecessary trip to the HA.

Benefits of Foreign Agent Local Routing to Mobile Networks

The Mobile IP - Foreign Agent Local Routing to Mobile Networks feature improves latency by allowing the FA to route traffic directly to mobile networks rather than routing through the HA. This feature is useful in scenarios in which a mobile router needs to receive high bandwidth traffic, such as streaming video, from a device on the local LAN of the FA. This feature can also be useful any time that the bandwidth between the FA and the HA is limited.

Specifies the mobility security associations for the mobile host, visitor, home agent, and foreign agent.

Troubleshooting Tips

Modifications to the home agent were made to support foreign agent local routing. You must be running Cisco IOS Release 12.3(7)T or higher for both the home agent and foreign agent for this feature to function properly. If the home agent version is lower than that, the foreign agent will report the following debug output from the debugipmobile command:

You can recognize this problem by observing that the debug output on the foreign agent only indicates the single network of 0.0.0.0 0.0.0.0.

Configuring an Access List

To restrict which mobile networks will have their local routes injected into the FA routing table, you may choose to configure an access list. You can configure either a named access list or a numbered access list. Perform one of the following tasks to configure an access list on the FA:

RFCs

RFCs

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

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Command Reference

The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the
Cisco IOS IP Mobility Command Reference at http://www.cisco.com/en/US/docs/ios/ipmobility/command/reference/imo_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at
http:/​/​tools.cisco.com/​Support/​CLILookup or to the
Cisco IOS Master Commands List .

ipmobileforeign-agentinject-mobile-networks

showipmobileglobals

Glossary

correspondentnode--A peer with which a mobile node or mobile router is communicating. A correspondent node may be either stationary or mobile.

foreignagent--A router on the visited foreign network that provides routing services to the mobile node while registered. The foreign agent detunnels and delivers packets to the mobile node or mobile router that were tunneled by the home agent of the mobile node. For packets sent by a mobile node, the foreign agent may serve as a default router for registered mobile nodes.

homeagent--A router on a home network of the mobile node that tunnels packets to the mobile node or mobile router while they are away from home. It keeps current location information for registered mobile nodes called a mobility binding.

mobilenetwork--A network that moves with the mobile router. A mobile network is a collection of hosts and routes that are fixed with respect to each other but are mobile, as a unit, with respect to the rest of the Internet.

mobilenode--A host or router that changes its point of attachment from one network or subnet to another. A mobile node may change its location without changing its IP address; it may continue to communicate with other Internet nodes at any location using its home IP address, assuming that link-layer connectivity to a point of attachment is available.

mobilerouter--A mobile node that is a router. It provides for the mobility of one or more entire networks moving together, perhaps on an airplane, a ship, a train, an automobile, a bicycle, or a kayak. The nodes connected to a network served by the mobile router may themselves be fixed nodes or mobile nodes or routers.